Among the biofuels, the most widely used is ethanol, in spark ignition engines (Otto cycle), as a compound mixed into gasoline or as relatively pure fuel. Ethanol has a high octane rating, that is, proper antiknock characteristics to spark ignition. Thus, it is possible to confer proper octane rating to gasoline, replacing tetraethyl lead, a toxic compound. When used in mixture with gasoline, ethanol is anhydrous, as presence of water can prevent formation of a stable mixture with gasoline. When used without any other mixture in Otto cycle engines, ethanol is hydrated. Ethanol is used in many countries mixed with gasoline, reaching in Europe and United States rates up to 85% in volume of ethanol in ethanol/gasoline blends (E85). In Brazil, pure hydrated alcohol is widely used.
However, ethanol has some disadvantages.
Ethanol contains low calorific power comparing to gasoline. On average, the energy content of hydrated ethanol is only 70% of energetic content of gasoline with 22% ethanol (blend supplied to Brazilian market).
Hydrated Ethanol has a higher corrosion rate when compared to gasoline.
Technologies allowing the use of ethanol or alcohol in compression ignition engines (diesel cycle) include blends and emulsions of ethanol and/or other alcohol in diesel fuel or oil fractions. Often such mixtures or emulsions use butanol or isobutanol as a co-solvent, an auxiliary with a polar character intermediate between ethanol and hydrocarbons, so as to increase the stability of mixture.
Mixtures tested and taken to market presently exhibit stability problems, as ethanol and diesel are poorly miscible. Many present a phase separation some time after mixture, such separation being aggravated by environmental conditions such as low temperatures, air humidity, etc. Surface degradation problems such as cavitation and corrosion occur frequently, due to physical separation between the compounds caused by the friction efforts and dynamic pressure differences found in the pumping system and fuel injection. Further, such mixtures still do not represent a completely renewable fuel, because use fossil fuels in large proportion.
Another current technology involves the mixture to hydrous ethanol of additives capable of increasing the ethanol explosivity, in order to allow its ignition by compression.
2-EHN and organic peroxides are conventionally used to increase diesel fuel explosivity, however, they are not used as additive to ethanol, because their added content versus increase in the cetane number curve tends to be asymptotic after 8% in volume of additive content, but does not reach the cetane number of about 42, which may be considered a requirement for a proper ignition of diesel fuel or hydrated ethanol.
All nitrates present stability problems (acidic or alkaline hydrolysis), especially in presence of water. Hydrated ethanol, by its water content, shows a tendency to hydrolyze, generating free acid which increases with storage period, leading to increased nozzle corrosion (e.g., for injector nozzles). Even in nitrate-free media, durability is reduced by the presence of steam in injector nozzle and exhaust valves. For this reason, the maintenance of systems for hydrated ethanol have a reduced time when compared to diesel systems. For example, the maintenance manual for Scania's ethanol-fueled buses for BEST Project indicates changing injector nozzles every 22,000 km, while the nozzle change in diesel systems occurs every 120,000 km.
Besides the durability problems related to hydrated ethanol, due to great difference of calorific power of ethanol related to diesel, there is an increase in the consumption measured as L/h of ethanol/L/h of diesel ratio between 1.5 and 2.0. This greater consumption, combined with cost of additives, tends to make economically impracticable ethanol projects, which are very important from an environmental point of view.
Another technology for ethanol employment on vehicle engines and equipment conventionally operating in diesel cycle consists on “ottolization”, that is, transformation of engines originally working in diesel cycle to run on the Otto cycle, by adaptation of a spark plug in a cylinder head of diesel engine. Such conversion, besides resulting in cost and time to be performed, being difficult to reverse, implies in consumption flow increases L/h ethanol L/h diesel above 2.0 once Otto cycle has an energy conversion efficiency about 30% lower than the diesel cycle of equivalent power.
Through searches performed on Brazilian and international patents databases, various patents were found, including those listed below.
Chinese patent with publication number CN 1016029686 and CN101434875 discloses options of hydrocarbons with ethanol.
Patent CN 101580743 discloses a diesel fuel or gasoline compound of fuel materials mixture, tar and solvents derivate from industrial or organic wastes, 10-50% of butanol, isopropanol, d-terc-butyl-p-cresol or their mixtures, 10-25% diene-ring iron, or kerosene, solvent oil, mineral oil, lubricating oil, vegetable oil or mixtures thereof. This patent does not employ substantially butanol as main fuel.
Patent CN 101402887 is a compound substantially composed of ethanol (75 to 90%) to act as diesel at low temperatures, containing, among other compounds, 2 to 10% butanol or isobutanol. Basically, butanol acts as co-solvent for several compounds.
Patent CN 101376848 describes an ethanol-diesel mixture with proportion between 60-85% of diesel. Butanol is used in the content between 0.5 and 1.5% as co-solvent to aid in the stability of resulting emulsion.
The American patent US 2009013591 show a fuel mixture including 15-95% of gasoline or diesel, from 5 to 85% of alcohol, among them butanol, characterized by the ethers use of glycerol as additive.
Chinese patent CN 101235325 reveals a diesel-methanol mixture, being diesel 23-50%, methanol 35-70% where two among various other components are isobutanol 0-3% and butanol 0-3%.
Chinese patent CN 101215483 presents a diesel-methanol mixture comprising between other compounds, 0.25-0.6% of terc-butanol.
Patent CN 1800313 reveals a gasoline emulsion with alcohols and dimethyl ether that may have 2-3% of 2-butanol.
Patent CN 1730619 presents a fuel emulsion that contains methanol, oil, diesel, terc-butanol, fatty acid ester of sorbic alcohol, polyoxyethylene and monomethyl polyethylene.
Patent CN 1796513 describes an additive to diesel comprising ethanol, ketones, silicones, n-butanol and benzyl alcohols.
Patent CN 1769398 presents a fuel with 65-80% methanol, which may contain, among others, 5-10% butanol.
Patent CN 1590515 describes a fuel formed by the diesel mixture, benzene, gasoline, butanol and ammonium salt of fatty acid.
Patent EP 0403516 presents a polyalkylene glycols additive to hydrated ethanol in the ration between 12-20%, however the examples show proper results in polyalkylene glycols contents exceeding 17% for conventional engines with typical compression ratio of 18:1.
U.S. Pat. No. 5,628,805 describes ethoxylated polyol to be added to hydrated ethanol in the ration between 5 and 10% v/v. Currently, this technology is being used in Stockholm (Sweden), and it is being tested in several cities of the world, applied in Scania engines, by means of the project BEST (BioEthanol for Sustainable Transportation). But to be used in the ration of 5%, it is required an engine specially projected for fuel, with a compression rate higher than that used in conventional diesel engines. While the conventional diesel engines compression rate is about 17:1, the Scania diesel engines compression rate dedicated to ethanol is about 24:1. This limits its use to dedicated engines, and prevents that the “flexfluel” technology is used, that is, neither fuel thus formulated could be used in a large base of existing conventional engines, or ethanol-dedicated engines could be used with proper diesel to conventional compression rates (oil, biodiesel, vegetable oil etc.).
U.S. Pat. No. 2,378,466 presents organic nitrates use such as ethyl nitrate, ethylene glycol dinitrate (EGDN), triethylene glycol dinitrate (TEGDN), tetraethylene glycol dinitrate (TetraEGDN), as additives capable of increasing the diesel ignition.
Recently, options of ethanol alternatives emerged from renewable sources. Among the options, 4-carbons alcohols, mainly n-butanol and isobutanol can be produced by renewable biotechnology process, with advantages such as a slightly lower calorific value than gasoline, higher solubility in hydrocarbons, lower corrosiveness, higher boiling and flash points, which makes handling and storage of the fuel safer and reduce evaporation losses. The conventional process for butanol production by microbiological fermentation is the process ABE (Acetone-Butanol-Ethanol), which uses sugars fermentation by the bacterium Clostridium acetobutylicum. Introduced in the early XX century by the industrial chemist, Zionist movement leader and first president of the State of Israel Chaim Weizmann, the process has its focus on the acetone production being used in large scale to obtainment of Cordite explosive (double based powder). Subsequently, the process was supplanted in terms of economic feasibility by the petrochemical process and fill into disuse.
A development line currently employed is the genetic modification of Clostridium genus that increases the ABE process productivity and selectivity to expand the butanol production. Such development line includes as n-butanol production processes, patents U.S. Pat. No. 5,753,474, US 2010143996, US 2010136641, CA 2699378, WO 2010024715, WO 2010024714, GB 2462642, WO 2010017230, US 2010036174, RU 2375451, CN 101595218, WO 2009149270, KR 2010019127, US 2010086982, WO 2009142541, GB 2459756, CN 101423815, CN 101250496, and JP 60172289.
The Canadian patent CA 2548221 reveals a new bacterium, Clostridium carboxidivorans, which can synthesize biofuels from CO, including ethanol and catalyze the acetate and butanol production. It also can directly ferment lignocellulose to produce ethanol or other substances.
Patents US 2009275787 and WO 2010031793 use modified Clostridium bacteria to produce n-butanol from glycerin. This process is of commercial interest, because great volumes of glycerin are obtained in the fatty acids transesterification (biodiesel production), and there is not demand to the planned volume of glycerin that must enter in the Brazilian market due to increased biodiesel content on diesel.
Patent US 2010093020 uses bacterium Enterococcus genus genetically modified for optimized production of butanol.
Patent WO 2009122192 uses in the butanol production, genetic bacteria modification of Bacillaceae family, preferably Geobacillus or Ureibacillus. 
Patent WO 2009082690 uses genetic code modification of many bacteria for butanol production.
Patents US 2010143985, US 2010129885, US 2010062505, WO 2009140159, WO 2009013159 present, for butanol production, a genetically modified yeast. The advantage of yeast is to use them normally for ethanol production, making easier the process adjustment for existing sugar and alcohol plants.
Canadian Patent CA 2691998 employs the bacterium or yeast genetically modified for butanol production.
Patent WO 2009105733 provides a photosynthetic process using plants, algae and blue-green algae that may produce butanol directly from CO2 and water. Thus, there is the direct carbon sequestration from atmosphere, with better energy use of the process, and competition reduction between the biofuels production process and food production.
Patent KR 20090025221 shows a process using algae to generate biomass, thus transforming it into alcohols or ketones, including butanol.
Patent WO 200900346 provides a process converting CO2 into gases, and which subsequently uses the fermentation of such gases to obtain products, including butanol.
Patents WO 2009103533, CA 2684860, WO 2009086423, and WO 2010037111 provide modifications on yeasts for isobutanol production.
Patent WO 2009149240 provides a production process for isobutanol from the biomass fermentation by bacteria species Escherichia coli. 
The following patents provide non-specified modified cells for butanol and ethanol production: WO 2009013160, US 2009176288, WO 2009082148, WO 2008124523, WO 2009059254, and WO 2008143704.
Patent WO 2009078973 presents genetic modifications on microorganisms for production of many value products, including butanol, from free fatty acids.
Patent CN 101358187 foresees gamma radiation to modify cells or protoplasts to increase the butanol yield.
Many processes apply conventional microorganisms of fermentation processes without genetic modification; however, with optimization of industrial process yield for obtaining butanol, or butanol from the fermentation broth, which increases yield, because the same low butanol contents make the fermentation media toxic for microorganisms producing alcohol.
Patents that disclose process changes: NL 10355651, KR 100556322, WO 2010011769, CN 201367402, US 2008274524, WO 2010000649, US 2010105115, WO 2009106835, WO 2009112335, WO 2009100434, CN 101475932, US 2009162912, WO 2009087680, WO 2009079362, CN 101418320, CN 101397236, CN 101429527, WO 2009062601, US 2009017514, CN 101363031, WO 2009021503, CN 101333545, WO 2009008616, WO 2008154301, CN 101302545, CN 101250561, WO 2008124490, CN 101333545, CN101457238, DE 102006060610 and WO 2009079213.
Patent CN 101165188 presents the butanol production from ground manioc or manioc starch.
Patent US 2010087687 presents a process for vegetable biomass, animal or municipal wastes exploitation, which includes butanol among the products.
Patent MX 2009006782 presents a process to produce biofuel, which includes biobutanol from enzymes.
Patent WO 2009128644 presents a metabolic network model for metabolic characteristics analysis of microorganisms producing butanol, and methods to select or change microorganisms to obtain high efficiency metabolic products.
Patents US 2010058654, JP 2009220105, WO 2009097312, KR 20090009330, JP 2008088140, and RU 2191769 present catalysts for processes that can convert ethanol produced from renewable sources in butanol.
Although it is desirable that the butanol become an economically feasible fuel produced from renewable and biological sources (so called biobutanol), there are other patented solutions for petrochemical processes to obtain butanol: patent US 2010048960 provides a process for producing butanol from butane.
Patent US 2009239275 presents a process to produce 2-butanol by petrochemical means.
Patent WO 2005108593 provides an enzymatic catalyst for production of 2-butanol from 2-butanone.
Patent KR 20080106516 describes a process for butanol production from butene.
Patent MX 2009008416 presents a production process of many alcohols, including n-butanol and isobutanol.
Below some patents are listed that describe fuels that use butanol as part of their compositions.
Patent US 2010005709 shows an ethanol mixture, isopropanol and sec- or terc-butanol, no more than 3% methanol and no more than 15% C5 or larger. The obtainment process is a petrochemical process Fischer-Tropsch type (obtaining alkanes from carbon monoxide and hydrogen), and the mixture is used as fuel to Otto cycle engines fuel (gasoline).
Patent US 2009277079 shows a mixture to be used with isomers butanol gasoline with good cold ignition.
Patent WO 2009120042 presents a process to chemically produce butyl butyrate from butyric acid and butanol from fermentation. Ester can be used as biodiesel.
Patent WO 2009114752 shows a process to use xenobiotic materials that are carbon sources, to produce biomass and/or biogas from microorganisms degrade carbon sources, and then using microorganisms to synthesize biofuels. One of biofuels cited is butanol.
Patent WO 2009106647 shows an engine with compression ignition comprising two injection systems, where one system injects diesel or biodiesel, and the other injects a fuel more volatile than diesel, such as hydrogen, LPG (Liquefied Petroleum Gas), natural gas, ethanol, propanol or butanol. Such biofuels hybrid system have been recently showed to the market by many companies, always with a using ration between two fuels next to 50%/50% with some disadvantages: requirement of two fuel tanks, separated transportation/supply logistic for two fuels, from a injection sophisticated control system variable as required power load, and the purchase by the user of injection system modification kit.
Patent US 2009151232 discloses a diesel composition having between 9 and 20% of butanol, 0.4% to 4% of nitrate or butyl nitrite, and the remaining base for light diesel, or uses a substantial amount (between 90.6 and 76%) of diesel derived from oil.
Patent CN 101402888 offers an additive compound and a diesel fuel of methanol containing, among other, 1 to 10% n-butanol. N-butanol acts as co-solvent, but the fuel is substantially composed of methanol, which has a low calorific power and is extremely toxic.
Patent KR 20090003146 shows a mixture to replace gasoline (Otto cycle engines), composed mainly of ethanol or methanol, containing among other, 5 to 8% of butanol.
Patent CN 101240199 shows a mixture of alcohol-ether (65-70%), where the alcohol is a mixture of methanol, butanol and acetone, and ether is a mixture of any two ethers including dimethyl ether, isopropyl ether or methyl terc-butyl ether (MTBE).
Patent US 2010005709 shows a process to produce alternative fuels, including obtaining synthesis gas from renewable sources, convert this gas into olefins with chain substantially between C2 and C4, and hydrolyze these olefins. The resulting mixture of alcohols has butanol, and should be mixed into gasoline.
Patent MX 2007010015 shows an alcohols mixture from C1 to C5 or C1 to C8, with more ethanol than methanol, with octane rating higher than ethanol, which could replace gasoline.
Patent CN 101085938 reveals a synthetic biological fuel with 10-50% of fuel derived from oil, such as naphtha, dimethyl ether and gasoline, 4.5-10% of one or more list that includes ether, acetone or butanol.
Patent CN 1884440 deals with the production of fatty acid ester (biodiesel) terc-butyl using terc-butanol as the transesterification reagent.
Patent JP 2004285346 comprises an alternative fuel to gasoline, ethanol compound, and at least two compounds from the group consisting of diisopropyl ether, methyl terc-butyl ether, ethyl terc-butyl ether, dipropyl ether, tert-butanol, dibutyl ether and diethyl ether.
Patent KR 20040044677 describes an alternative fuel composed of 50-80% of mixed liquid extract of coal extracted from bituminous coal, 10-20% of ethanol or methanol from coal liquefaction, 5-15% of n-butanol extracted from coal liquefaction, and 5-10% and 5-10% toluene extracted from the liquefaction of coal.
Patent KR 20020009543 presents alcohol-based fuels to replace gasoline compound, among others, 5-15% butanol.
Patent KR 20030006529 describes a fuel to internal combustion engines, Otto cycle, compound, among others, 3-7% butanol.
Patent RU 2148075 presents based fuel compositions, containing 0.0065-0-0.0075% of “oligoetilhidreto” siloxane and 0.0025-0.0035% by weight of butanol.
Patent WO 9324593 discloses a diesel fuel, containing between 10 and 35% of ethanol in diesel mixture, also containing butanol and alkyl peroxide.
Patent KR 930011071 describes an emulsion fuel of 1000 parts of oil (gasoline?), 15-70 parts of siloxane or “oxosilano”, 100-300 parts of butanol, 3-7 parts of methanol, 10-20 parts of polyethylene glycol and 1-3 parts of non-ionic surfactant.
Patent JP 2022388 provides a fuel in alcohol emulsion form (methanol, ethanol, or butanol), benzene, toluene or xylene, and an aromatic rich fraction from the catalytic cracking fluid of oil refinery.
European patent EP 0171440 describes a fuel for engine basically based in a hydrocarbons compound, which additionally contains alcohols and optionally ethers, ketones, aromatics, additives and lead compounds that may contain 0-10% butanol.
Patent CA 1221539 describes a stable composition of gasoline and ethanol, containing an additional alcohol, that may be, among others, n-butanol and isobutanol.
U.S. Pat. No. 4,526,586 describes microemulsions from vegetable oil, a C1-C3 alcohol, water and 1-butanol as non-ionic surfactant.
Patent GB 2090612 describes a mixture for use of diesel comprising between 10 and 60% in gas oil, 10-60% of a C1-C8 alkyl ester, C12-22 fatty acid and 10-50% of a mixture which contains at least n-butanol and acetone.
U.S. Pat. No. 4,398,920 deals with a fuel a mixture containing: (a) gasoline, gas oil, or fuel oil, (b) a mixture of butanol and acetone, optionally containing isopropanol and/or ethanol; and (c) methanol, where the mixture butanol/acetone (b) is prepared by proper organisms fermentation such as bacteria or fungi.
U.S. Pat. No. 4,368,056 describes a fuel formed by mixing butanol obtained from fermentation and glycerides obtained from a fermentation process where the substrates are industrial wastes such as cheese yeast, corn cobs, wood chips etc.
U.S. Pat. No. 4,300,912 describes a synthetic fuel consisting of macromolecules of long chain formed by connection by methanol distillation, butanol and kerosene oil with colloidal stabilizer.